Overview

Audio watermarking schemes play very important role in digital copyright protection, authentication, indexing, synchronization of audio and video, and so on (Cox et al. 2002). Available studies on audio watermarking is far less than that of image watermarking or video watermarking since audio watermarking is more difficult to develop than image and video. Watermarking is a process of adding noise in any manner to the host signal. Unfortunately, human ear is far more sensitive than other sensory motors in terms of noise detection capability. One of the difficulties of audio watermarking comes from the sensitivity to embedding noise. However, during the last decade audio watermarking studies have also increased considerably. Those studies have contributed much to the progress of audio watermarking technologies. This chapter surveys those studies and classify them into four categories: spread-spectrum scheme, two-set scheme, replica scheme, and self-marking. First one embeds pseudorandom sequence and detects by calculating auto-correlation. The spread-spectrum scheme belongs to this class. Second one exploits the differences between two or more sets. The patchwork scheme belongs to this category. Third one uses the replica of the original audio clips both in embedding and detection phases. The replica modulation is an example of this class. Last one is self-marking scheme which can be used especially for synchronization or for robust watermarking, for example, against time-scale modification attack. Such four seminal works have improved watermarking schemes remarkably. However, more sophisticated technologies are required,...